October 19, 1999
01:00 AM (EDT)

News Release Number: STScI-1999-39

The "Rotten Egg" Nebula: A Planetary Nebula in the Making

October 19, 1999: This oddly shaped object is an aging, Sun-like star near the end of its life. The Hubble telescope's infrared camera, called the Near Infrared Camera and Multi-Object Spectrometer, captured a fleeting phase in the death march of this star. In these pictures, a red giant star is transformed into a planetary nebula, the glowing remnants of a dying star. The star is shrouded in dust and gas in the center of these pictures. The "wings" of material, called a nebula, are dust and gas cast off by the declining star.

Q & A: Understanding the Discovery

1.
What do the images of this dying star tell astronomers?

The star is blowing out gas and dust in two opposite directions. These blasts of gas are
traveling at speeds up to 450,000 mph. The fast-moving gas and dust are forming several
thin streamers [on the right of both images]. A jet of material can be seen in the left lobe.
On the right, wisps of material in jet-like streamers appear to strike dense blobs of gas. By
studying these structural details, astronomers will gain a better understanding of the final
stages in the lives of stars like our Sun.

2.
Why do astronomers need an infrared camera to take pictures of this object?

An infrared camera "sees" through dust and gas to capture more details of the nebula's
structure. Unlike most visible light, infrared light is not absorbed by dust.

3.
Why are there two pictures of the same object?

The two pictures tell different stories about the last gasps of this dying star. The
black-and-white image shows more clearly the faint detail and structure in the nebula. The
color picture reveals that the composition and temperature of the material ejected from the
star varies.

4.
Why is this object called the "Rotten Egg" Nebula?

Astronomers have dubbed the object the "Rotten Egg" Nebula because of the large
amount of sulfur compounds found in the gas surrounding the star. The object's "proper"
name is OH231.8+4.2, and it resides in the constellation Puppis.